Amp meter reading backwards

^^^^^^^^^^^This^^^^^^^^^^^^^^

Can also do some quick testing to confirm its a wire crossed and not some other issue.
1. Engine off.
Open the door (dome light) and step on the brake (brake lights). It should show about 5 amps discharge.
if the needle movement is hard to see, shut the door, turn on the headlights.

2. Engine running at fast idle. (anywwhere from 1250 rpm to 1600 rpm depending on the step)
Check the voltages at the battery post, at the alternator output stud, at the ballast resisitor ignition terminal (blue wire).
At the same time check the ammeter.
This is just to eliminate the possibility the alternator output wire isn't well connected to the main splice.